JPH03162641A - Force detecting device - Google Patents

Abstract

PURPOSE:To enable accurate force detection which is not affected by a leak current by forming P-N junction in a semiconductor substrate by using a reverse conductive layer formed on the reverse surface side of the substrate. CONSTITUTION:The force detecting device consists of the semiconductor substrate 10, a connection layer 20, and a strain inducer 30. A gate resistance 11 is a resistance element obtained by diffusing P type impurities in the N type semiconductor substrate 10 and has piezoelectric resistance effect which varies in electric resistance by mechanical deformation. Then the P type reverse conductive layer 13 is formed on the reverse surface side of the semiconductor substrate 10. Then the semiconductor substrate 10 and strain inducer 30 are put in a eutectic coupled state through the connection layer 20 made of metal, so the semiconductor substrate 10 and strain inducer 30 become conductive. In general, the strain inducer 30 is screwed to a device housing, so when a leak current flows from a gauge resistance 11 to the device housing, so it exerts important influence upon the measurement accuracy. This leak current can be cut off by a potential barrier formed of the P-N junction between a substrate area 12 and the reverse conductive layer 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a force detection device, and particularly to a device that exerts force by changing the electrical resistance of a resistive element formed on a semiconductor substrate.

[Conventional technology]

Generally, a device that detects a force acting on a certain point of action indirectly detects the stress strain produced by the action of this force. Detection of stress strain is carried out by installing a strain gauge or other strain gauge at each part of the strain body that generates stress strain due to the action of force, and determining changes in the resistance value of this detector as ijPI. .

Recently, a technology has been proposed in which resistance elements with a viezoresistance effect, in which electrical resistance changes due to mechanical deformation, are arranged on a semiconductor substrate, and force is generated from changes in the resistance value of the resistance elements. ing. The action of force causes mechanical strain on the semiconductor substrate, and the resulting change in the resistance value of the resistive element is electrically exposed.

For example, in Japanese Patent Application Laid-Open No. 63-266329,
By forming multiple resistance elements at predetermined positions along the X-axis direction and the Y-axis direction on a substrate spread out on a flat surface, and assembling these resistance elements into a unique bridge circuit, the A technique is disclosed in which forces and moments acting around each axis are expressed as changes in bridge voltage. Furthermore, in the specification of Japanese Patent Application No. 1-105482,
An invention is disclosed in which a connection layer is provided between a semiconductor substrate and a strain body, and the strain body and the semiconductor substrate are connected by eutectic bonding. In this manner, the semiconductor substrate can be protected from damage by once applying an external force to the strain-generating body and transmitting a portion of the external force acting on the strain-generating body to the semiconductor substrate.

[Problem to be solved by the invention]

Generally, a metal is used as a strain element, but if this metal is connected to a semiconductor substrate through eutectic bonding, the strain element becomes electrically conductive from the semiconductor substrate, so the PN withstand voltage of the resistance element formed on the substrate increases. When the resistance is low, a leakage current flows between the resistance element and the strain body. This leakage current causes fluctuations in the measured force value, causing an adverse effect of preventing accurate measurement.

In order to eliminate such problems, a method of forming an insulating film in the connection layer between the semiconductor substrate and the strain-generating body is disclosed in Japanese Patent Application No.
It is proposed in the specification of No. 105482. However, it is technically difficult to form an insulating film between a semiconductor substrate and a substrate while maintaining a bond between them.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a force detection device that can perform accurate force detection without the influence of leakage current while maintaining good connection between a metal erected body and a semiconductor substrate through eutectic bonding. .

[Means to solve the problem]

(1) The first invention of the present application includes a semiconductor substrate of a first conductivity type, and an impurity formed on the upper surface of the semiconductor substrate and containing an impurity of a second conductivity type opposite to the first conductivity type. A resistance element having a property of changing resistance; a metal strain-generating body having a support part and an action part and causing mechanical deformation in the resistance element based on displacement of the action part with respect to the support part; and a semiconductor. a connecting layer that is filled between the lower surface of the substrate and the strain-generating body and forms a co-bonding with the semiconductor substrate and the strain-generating body, respectively; In a force detection device that detects a change in resistance, a reverse conductive layer containing impurities of a second conductivity type is formed on the lower surface side of a semiconductor substrate.

(2) The second invention of the present application includes a semiconductor substrate of a first conductivity type, and an impurity formed on the upper surface of the semiconductor substrate and containing an impurity of a second conductivity type opposite to the first conductivity type, and which generates electricity by mechanical deformation. A resistance element having a property of changing resistance; a metal strain-generating body having a support part and an action part and causing mechanical deformation in the resistance element based on displacement of the action part with respect to the support part; and a semiconductor. a connecting layer that is filled between the lower surface of the substrate and the strain-generating body and forms a common bond with the semiconductor substrate and the strain-generating body, respectively; In a force detecting device that detects a change in resistance, a voltage applying means is provided to apply a reverse bias to a PN junction existing at the boundary of a region where a resistive element is formed.

[For production]

(1) According to the first invention of the present application, a PN junction is formed in the base slope by the reverse conductive layer formed on the lower surface side of the semiconductor substrate, and an electric current flows from the resistance element to the strain body due to the electrical barrier caused by this PN junction. Leakage currents are prevented. Furthermore, since this reverse conductive layer maintains the crystal structure of the original semiconductor substrate as it is, eutectic bonding can be maintained up to the strain body via the connection layer.

(2) According to the second invention of the present application, a reverse bias is applied to the PN junction existing at the boundary of the region where the resistance element is formed. The leakage current flowing from the resistance element to the strain body is blocked by the potential barrier caused by this direction bias. Since there is no need to form an insulating film between the semiconductor substrate and the strain body, a eutectic bond between the semiconductor substrate and the strain body can be easily obtained via the connection layer.

[Practical]

The present invention will be described below based on illustrated embodiments.

First Embodiment FIG. 1(a) is a side sectional view of a force detection device according to an IFI1 according to the first embodiment of the present invention. This device is composed of a semiconductor substrate 10, a connection layer 20, and a strain body 30. The semiconductor substrate 10 is made of N-type silicon,
A region in which P-type impurities are partially diffused is formed. An enlarged side sectional view of the semiconductor substrate 10 is shown in FIG.

The gauge resistor 11 formed on the top surface is a resistance element obtained by diffusing P-type impurities into the N-type semiconductor substrate 10, and has a piezoresistance effect in which electrical resistance changes due to mechanical deformation. In FIG. 1, only two gauge resistors 11 are shown, but in reality, more gauge resistors are arranged at predetermined positions and facing in predetermined directions. A feature of the first invention of the present application is that a P-type reverse conductive layer 13 is formed on the lower surface side of the semiconductor substrate 10. The remaining N-type region becomes the substrate region 12. In this way, the semiconductor substrate 10 is composed of the gauge resistor 11, the substrate region 12, and the reverse conductive layer 13.

The strain body 30 is made of Kovar (an alloy of iron, cobalt, and nickel) and has a substantially disk shape.

An acting portion 31 located at the center is shaped to protrude from the center of the disk, and an external force to be detected is applied to this acting portion 31. This action portion 31 is connected to a support portion 33 located on the outer periphery via a flexible portion 32. The support portion 33 is fixed to the main body of the device.

The flexible portion 32 is a portion that is made flexible by reducing its thickness. Therefore, when an external force is applied to the acting portion 31, the flexible portion 32 is bent, causing the acting portion 31 to be displaced with respect to the support portion 33.

The connection layer 20 is a layer that is filled between the semiconductor substrate 10 and the strain body 30 and connects them.

The characteristics of this connection layer 20 are that the connection layer 20 and the semiconductor substrate 10 are
and between the connection layer 20 and the strain-generating body 30 are connected by eutectic bonding. When the two are connected by such a connection layer 20, the semiconductor substrate 10 to the strain body 30 are connected by the crystal structure.

Moreover, since the connection layer 20 is a layer filled between the two,
A uniform connection is made with no gaps. Therefore, the mechanical deformation generated in the strain body 30 is accurately transmitted to the gauge resistor 11 on the semiconductor substrate 10, making it possible to accurately measure external force.

FIG. 2 is a diagram showing a method of manufacturing the device shown in FIG. 1. First, a P-type impurity is diffused into a predetermined position on the upper surface of an N-type silicon semiconductor substrate 10 to form a gauge resistor 11 . Thereafter, wiring made of aluminum or the like is applied to each gauge resistor 11, but the explanation is omitted here.

Subsequently, P-type impurities are also diffused on the lower surface of the semiconductor substrate 10 to form a reverse conductive layer 13. On this reverse conductive layer 13,
The gold layer 21 is deposited by the Subanota method or vapor deposition process.
form. On the other hand, a chromium layer 22 is formed on the surface of the strain-generating body 30 by sputtering, and a gold layer 23 is formed thereon by sputtering or vapor deposition. Then, an alloy foil 24 of gold and tin is prepared, and with the alloy foil 24 sandwiched therebetween, a load is applied between the semiconductor substrate 10 and the strain body 30 to rub them together. At this time, set the temperature to 280-320
℃. In other words, so-called scrubbing is performed. As a result, eutectic bonding occurs between the gold layer 21 and the alloyed material 24, and eutectic bonding also occurs between the gold layer 23 and the alloy 7324. Finally, a connection layer 20 composed of layers 21 to 24 is formed between the semiconductor substrate 10 and the strain body 30, and all are connected by eutectic bonding. Note that the chromium layer 22 is a layer for improving the connection between the strain body 30 and the gold layer 23, and a Nisokel layer may be used instead of the chromium layer. Alternatively, a nickel layer may be further formed on the chromium layer. Moreover, as the alloy foil 24, a eutectic alloy of gold and silicon, etc. may be used instead of an alloy of gold and tin. In short, any material may be used as the alloy 24 as long as it forms a eutectic alloy.

The main point of the first invention of the present application is that in a force detection device having such a structure, by forming the reverse conductive layer 13,
The purpose is to prevent leakage of electric current from flowing from the gauge resistor 11 to the strain body 30. As described above, since the semiconductor substrate 10 and the strain-generating body 30 are connected together by the connection layer 20 made of metal, the semiconductor substrate 10 and the strain-generating body 30 are electrically connected. Generally, the strain-generating body 30 is screwed to the device casing, so if a leakage current flows from the gauge resistor 11 to the device casing, it will seriously affect measurement accuracy. In this device, this leakage current can be blocked by a potential barrier formed by a PN junction formed between the base temporary region 12 and the reverse conductive layer 13.

Note that when manufacturing this device, it is preferable to prevent the connection layer 20 from wrapping around the side surface of the semiconductor substrate 10.

As in the example shown in FIG.
If the leakage current goes around the side surface of the semiconductor substrate 10 and comes into contact with the base temporary region 12 and the connection layer 20, a leakage current will flow from the side surface of the semiconductor substrate 10, which is not preferable.

Second Embodiment Next, a force detection device according to an embodiment of the second invention of the present application will be described. First, the basic principle of the present invention will be explained using FIG. 4. FIG. 4 is a cross-sectional view (shown by hatching) of the semiconductor substrate 10 with a corresponding circuit diagram added thereto. In this device, as in the device of the first embodiment described above, a reverse conductive layer 1 is provided on the lower surface side of the semiconductor substrate 10.
There is no need to form 3. In other words, semiconductor base t! L
The ten N-type substrate regions 12 may be eutectically bonded to the connection layer 20 as they are. Since this device is a device that measures external force by utilizing the fact that the electrical resistance of the gauge resistor 11 changes due to the external force transmitted from the strain body 30, it is possible to measure the electrical resistance of the gauge resistor 11. An outgoing circuit is required. In this example, a first power source 41 is provided for applying a detection voltage Vref to two gauge resistors 11 connected in series. The current from the power source 41 flows through detection current paths indicated by points A, B, C, and D in the figure. Actually, as will be described later, a bridge circuit is formed by several gauge resistors l1.

A feature of the present invention is that a second power source 42 is further provided. This power source 42 is connected to the above-mentioned electric waterfall paths A and B.
, C, and D, it has a function of applying a bias voltage E to a point F in the substrate region 12. Here, bias voltage E≧detection voltage Vref. Now, gauge resistance 1
Considering the boundary portion of 1, a PN junction is formed between it and the base temporary region 12.

Furthermore, the bias voltage E has a polarity that provides a reverse bias with respect to this PN junction. Therefore, the leakage current flowing from the gauge resistor 11 to the substrate region 12 is
This is blocked by a potential barrier caused by this reverse bias. This is the basic principle of the invention. According to this method,
Even if the substrate region 12 and the strain region (*30) are electrically conductive, leakage current formation can be prevented.

FIG. 5 is a side sectional view showing a specific wiring example of a force detection device according to an embodiment of the present invention. Support part 3 of strain body 30
A wiring hole 34 (only two wiring holes 34a, 34b are shown in the figure) is provided in 3, wiring pins 35a, 35b are passed through these wiring holes 34a, 34b, and bonding wires 36a,
36b provides wiring to the strain body 30 and the semiconductor substrate 10. If a reverse bias voltage E is applied to the lower end of the wiring pin 35a in the diagram, the semiconductor substrate 1
This reverse bias E is applied to the lower surface of 2, that is, point F in FIG. Of course, the bonding wire 36a may be directly connected to the connection layer 20 or the semiconductor substrate IO. On the other hand, if a detection voltage Vref is applied to the lower end of the wiring pin 35b in the figure, this voltage Vref is applied to the gauge resistors r1 to r4 formed on the upper surface of the semiconductor substrate 10 by the bonding wire 36b. The four gauge resistors r1 shown in this figure
~r4 is for exposing the moment force generated at point P when a force in the direction of the arrow is applied to the lower end of the acting portion 31.

FIG. 6 is a specific circuit diagram of a constant voltage drive type for operating the device shown in FIG. 5. In the circuit diagram of Figure 4, 2
Although two power supplies 41 and 42 are shown, in the specific circuit shown in FIG. 6, the power supply 51 or two ffiF! ．． 41.
It will also serve as 42. That is, 7[[51 generates a voltage E, and by applying this voltage E to the series circuit of the Zener diode 52 and the low resistor 53, a constant voltage Vref for detection is obtained at the node G. This voltage Vref
is given to a bridge circuit constituted by gauge resistors r1 to r4 through an operational amplifier 54.The output of this bridge circuit connects a differential circuit constituted by operational amplifiers 55 and 56 and an operational amplifier 57. Then, it appears at the output terminals H and I. On the other hand, the reverse bias voltage E appearing at the terminal F is the base !i2 nR region 1 of the semiconductor substrate lO.
2 (corresponding to point F in the fourth mother). With this configuration, the force acting in the direction of the arrow at point P in FIG. 5 is exposed as a voltage between output terminals H and 1. Moreover, the reverse high-ass voltage E is applied to the base temporary region 12 with respect to the cage resistors r1 to r4, and leakage current is prevented.

FIG. 7 is a specific circuit diagram of a constant current drive type for operating the device shown in FIG. 5. The components are the same as the circuit shown in FIG. 6, but the connections are somewhat different. In this circuit, constant current I is always supplied to the bridge circuit. Also, it is necessary to design the bridge circuit so that the voltage at one end J is lower than the terminal voltage at F.

Two specific circuit diagrams have been explained above, but the present invention is, in short, any circuit that can supply a bias voltage in the opposite direction to the PN junction that exists at the boundary of the gauge resistor. You may use it.

Other Examples Although the first and second inventions of the present application have been explained using several practical examples, the present invention is not limited to these examples only, and can be applied in various ways. is possible. For example, in the example shown in Fig. 5, only the arrangement of gauge resistors for detecting force in one direction is shown, but in order to detect force in multiple directions, a large number of gauge resistors are placed at predetermined positions and at predetermined positions. The present invention is also applicable to devices that are arranged in this direction and constitute a large number of bridges. The arrangement of gauge resistors, bridge configuration, etc. for such a multi-directional component force detection device is disclosed, for example, in Patent Cooperation Treaty application No. PCT/JP88/00395.

Furthermore, in the above embodiment, a type in which a P-type impurity region is formed in an N-type semiconductor substrate was explained, but P-type and N-type impurity regions are formed in an N-type semiconductor substrate.
The present invention is also applicable to a type of device in which the type is completely replaced.

〔Effect of the invention〕

(1) According to the first invention of the present application, since a PN junction is formed in the substrate by the reverse conductive layer formed on the lower surface side of the semiconductor substrate, leakage flowing from the resistance element to the strain body due to the potential barrier caused by the PN junction Current can be blocked. Moreover, since this reverse conductive layer maintains the crystal structure of the original semiconductor substrate, it is possible to maintain eutectic bonding through the connection layer to the strain element, accurately transmitting external force to the resistance element. This allows for accurate measurements.

(2> According to the second invention of the present invention, since a reverse bias is applied to the PN junction existing in the A field of the region where the resistive element is formed, ?1 due to this reverse bias?
Leakage f flowing from the resistance element to the strain body due to the S-position barrier
tSiA can be prevented. According to this method,
Since there is no need to form an insulating film between the semiconductor substrate and the strain body, a eutectic bond between the semiconductor substrate and the strain body can be easily obtained through the connection layer, and external forces can be accurately resisted. It can be transmitted to the element, making accurate measurement possible.

[Brief explanation of the drawing]

FIG. 1(a) is a side sectional view showing the structure of a force detection device according to an embodiment of the first invention of the present application, and FIG. 1(b) is the same view (a).
FIG. 2 is a diagram showing a manufacturing method of the device shown in FIG. 1, FIG. 3 is a diagram showing an inappropriate example of the manufacturing method of FIG. 2, and FIG. Diagram showing the basic principle, 5th
The figure is a side sectional view showing the structure of a force detection device according to an embodiment of the second invention, and FIGS. 6 and 7 are circuit diagrams showing a circuit used in the device shown in FIG. 5. l○...Semiconductor substrate, 11...Gauge resistance, 12.
... Substrate region, 13... Reverse conductive layer, 20... Connection layer, 21... Gold layer, 22... Chromium layer, 23... Gold layer,
24...Gold and tin alloy foil, 30...Strain element, 31.
...Action part, 32...Flexible part, 33...Support part, 34
a, 34b...Wiring hole, 35a, 35b-=wiring bin, 36a, 36b...Bonding wire, 41...
- First power supply, 42... Second power supply, 51... Power supply,
52... Zener diode, 53... Resistance element,
54-57... operational amplifier.

Claims (2)

[Claims] (1) A semiconductor substrate of a first conductivity type, which is formed on the upper surface of this semiconductor substrate and contains impurities of a second conductivity type opposite to the first conductivity type, and has a property that electrical resistance changes with mechanical deformation. a metal strain-generating body that has a support part and an action part and causes mechanical deformation in the resistance element based on displacement of the action part with respect to the support part; a connection layer that is filled and formed between a lower surface and the flexural body and forms a eutectic bond with the semiconductor substrate and the flexural body, respectively; What is claimed is: 1. A force detection device that detects a change in electrical resistance of an element, characterized in that a reverse conductive layer containing an impurity of the second conductivity type is formed on the lower surface side of the semiconductor substrate. (2) A semiconductor substrate of a first conductivity type, which is formed on the upper surface of this semiconductor substrate and contains an impurity of a second conductivity type opposite to the first conductivity type, and has a property that electrical resistance changes due to mechanical deformation. a metal strain-generating body that has a support part and an action part and causes mechanical deformation in the resistance element based on displacement of the action part with respect to the support part; a connection layer that is filled and formed between a lower surface and the flexural body and forms a eutectic bond with the semiconductor substrate and the flexural body, respectively; A force detection device that detects a change in electrical resistance of an element, characterized in that a voltage application means is provided for applying a reverse bias to a PN junction existing at a boundary of a region where the resistance element is formed. Force detection device.